Objective This study took modified biochar with bamboo vinegar as the research object and analyze the effects of bamboo vinegar modification on the physical structure and chemical properties of biochar. The effects of soil improvement were discussed when the modified biochar with bamboo vinegar was added into mild alkalized fluvo-aquic soil in order to provide theoretical support for similar saline alkali land improvement and remediation in the future.

Method Modified biochar with different acidity was obtained by using bamboo vinegar of different concentrations. Different modified biochar treatments were used to improve the mildly alkaline alkalized fluvo-aquic soil. Group B0 was treated with modified biochar with undiluted stock solution, Group B2 was treated with modified biochar with twice diluted bamboo vinegar solution, group B5 was treated with modified biochar with five-time diluted bamboo vinegar solution, group B10 was treated with modified biochar with 10-time diluted bamboo vinegar solution added, and group B was treated with unmodified biochar added. The improvement effect and its influence on the growth of Pakchoi were studied.

Result After modified by bamboo vinegar, the pH of biochar became acidic or neutral, the specific surface area and pore volume increased significantly (P < 0.05), but the average pore size decreased significantly (P < 0.05), among which the B0 group had the largest change. After the application of modified biochar, soil pH decreased to a certain extent. After the addition of B2 and B5 groups to soil, the ESP and total salt content of soil decreased significantly (P < 0.05), in which the soil ESP decreased by 17.7% and 39.6%, and the total salt content decreased by 34.6% and 38.5%, respectively. Soil sucrase, alkaline phosphatase, urease and catalase were significantly (P < 0.05) increased. In addition, compared with the blank soil control group without biochar and group B, after adding soil to groups B2, B5 and B10, the germination percentage, plant height, leaf area and fresh weight of Pakchoi increased significantly (P < 0.05) in the range of 17.1%-48.6%, 8.6%-36.4%, 27.9%-49.9% and 18.9%-63.7%, respectively.

Conclusion The results showed that the modified biochar with 5-time and 2-time dilution of bamboo vinegar had a good improvement effect on mild alkalized fluvo-aquic soil, which can serve as an excellent soil conditioner for mild saline-alkali land improvement.